1. Field of the Invention
The present invention relates to a manufacturing method of a micro structure such as a micro gear or a microscopic optical component manufactured by a laminated formation method or a die for molding of such a component. In particular, the invention relates to a manufacturing method of a micro structure capable of laminating very thin films at a high transfer rate.
2. Description of the Related Art
In recent years, the laminated formation method has spread rapidly as a method for forming a computer-designed three-dimensional object having complex shape in a short period (i.e., a period short enough to meet an early appointed date of delivery). Three-dimensional objects formed by the laminated formation method are used as models (prototypes) of components of various apparatus to check whether their operations and shapes are proper. In the past, in many cases, components to which this method were applied were of relatively large sizes, that is, on the order of centimeters or larger. However, in recent years, there has occurred demand for application of this method to micro parts produced by the precision machining such as micro gears and microscopic optical components. Prior art references relating to this technology are JP-A-2000-238000 (patent document-1) and JP-A-11-28768 (patent document-2).
FIGS. 7A-7C to FIGS. 9A and 9B show a manufacturing method of a micro structure that is described in patent document-1. First, as shown in FIG. 7A, a silicon wafer as a substrate 101 is prepared and a polyimide release layer 102 is formed on the surface of the substrate 101 at a thickness of 2 to 5 μm by spin coating.
Then, as shown in FIG. 7B, an 8-μm-thick A1 thin film 103 is deposited on the release layer 102 by sputtering and a resist 104 is formed thereon. After a photolithography step, as shown in FIG. 7C the A1 thin film 103 is etched into plural thin-film patterns 105a, 105b, and 105c having partial sectional shapes of a desired micro structure. A resulting substrate is called a donor substrate 106.
Then, as shown in FIG. 8, the donor substrate 106 is fixed to an xyθ stage 107 that is provided in a vacuum chamber 110 and can be moved in the x-axis and y-axis directions and rotated about the z axis (i.e., in the θ direction). A target substrate 109 is fixed to a z stage 108 that can be moved in the z-axis direction. Then, FABs (fast atom beams) that are Ar neutral beams are emitted from particle beam emission ends 111 and 112 and applied to the surfaces of the donor substrate 106 on the xyθ stage 107 and the target substrate 109 on the z stage 108, whereby oxide films, impurities, etc. on the surface of the donor substrate 106 and the target substrate 109 are removed to produce clean surfaces.
Subsequently, as shown in FIG. 9A, the surface of the target substrate 109 is brought into contact with the surface of the first thin-film pattern 105a and pressed against it with a load of 50 kgf/cm2 for 5 minutes, whereby the target substrate 109 and the first thin-film pattern 105a are joined to each other strongly.
Then, as shown in FIG. 9B, the z stage 108 is elevated. Since the joining of the target substrate 109 and the first thin-film pattern 105a is stronger than the adhesion between the first thin-film pattern 105a and the release layer 102 on the donor substrate 106, the first thin-film pattern 105a is transferred from the donor substrate 106 to the target substrate 109.
Then, the xyθ stage 107 is moved by a prescribed pitch and positioning, FAB illumination, and transfer steps are repeatedly executed for the second thin-film pattern 105b and then for the third thin-film pattern 105c in the same manner as done for the first thin-film substrate 105a as shown in FIGS. 8, 9A and 9B, whereby a micro structure is completed. Then, the target substrate 109 is removed from the z stage 108 and the necessary micro structure is separated from the target substrate 109.
The conventional manufacturing method of a micro structure described in patent document-2 is as follows. A release layer is formed on a substrate and plural thin-film patterns having prescribed two-dimensional patterns are formed on the release layer. The release layer is etched back at a prescribed depth to form recesses. The thin-film patterns are peeled off the release layer and laminated (joined together) on a stage, whereby a micro structure is obtained. With this manufacturing method, even if particles such as fragments of glass or an Si wafer as a substrate, peeled pieces of metal, or a fine powder exist between the substrate and the stage, the surface contact between the state and the thin-film patterns is not obstructed.
However, in the conventional manufacturing method of patent document-1, if a thin-film pattern 105 is too thin, the thin film pattern 105 is buried in the release layer 102 and the top surfaces of the thin-film pattern 105 and the release layer 102 are made flush with the bottom surface of the target substrate 109. A load from the target substrate 109 is imposed uniformly on the thin-film pattern 105 and the release layer 102. Contrary to the intention of applying a load to the thin-film pattern 105 to join and transfer the thin-film pattern 105 to the target substrate 109, as shown in FIG. 10 a portion of the release layer 102 is raised in a region close to the circumference of the thin-film pattern 105 and the top surface of the raised portion 102a becomes flush with that of the thin-film pattern 105. The load imposed on the thin-film pattern 105 becomes insufficient, resulting in insufficient joining and transfer.
On the other hand, in the conventional manufacturing method of patent document-2, although the release layer is etched back, the etch-back is performed to decrease the transfer yield reduction due to particles. Therefore, the conditions relating to the thicknesses of the thin-film patterns and the release layer are different from the conditions of the problem to be solved by the invention. Therefore, this manufacturing method cannot solve the problem that arises when the height of a raised portion of the release layer in a region close to the circumference of a thin-film pattern is greater than or equal to the thickness of the thin-film pattern in the transfer step.